Cast metal article and method of casting same



M y 1941. A. F. 9. THOMPSON 2,242,554

CAST METAL ARTICLE AND METHOD OF CASTING SAME Filed June 17, 1940 INVENTOR Patented May 20, 1941 CAST METAL ARTICLE AND METHOD F CASTING SAME Arthur F.- D. Thompson, Detroit, Micln, asslgnor to Michigan Steel Casting Company, Detroit, Mich, a corporation of Application June 17, 1940, Serial No. 340,895 9 Claims. (Cl. 22-200) This invention relates to casting of metal articles having ribs, braces, bars or other construction members which meet or intersect, the principal object being the provision of 'a method of casting such articles whereby to eliminate shrinkage cavities, cracks or other defects and which will not detract from the strength of the finished article, as well as to an improved cast article formed in accordance therewith.

Objects of the invention include the provision of a method of casting metal articles having ribs, braces, bars or other construction members which meet or intersect, including the provision of cored openings in the articles extending perpendicular to the line of intersection of the ribs,

braces, bars or other members and are spaced along the line of intersection from the edges of such members; the provision of a method of casting articles of the type described including the steps of providing a cored opening through said members intermediate the length 'of intersection thereof and increasing the thickness of the members in a plane perpendicular to the line of intersection thereof tocompensate for the metal eliminated by cored opening; and the provision of the steps in the method of casting an article including intersecting webs or other members of approximately equal metal thickness comprising the provision of cored members intermediate the length of the line of intersection of the members and spaced from one another and the edges ofthe members at opposite ends of the line of intersection between them by-distances approximately equal to the thickness of the members, depending on their shape, and practical core dimensions and proportions.

Other objects of the invention include the provision of an integral cast metal article having ribs, braces, bars or other construction members which meet or intersect one another, having openings therein transverse to the line of intersection between them and intermediate the edges of the said members at Opposite ends of the line of intersection between them; the provision of cast metal articles of the type described in which a radius or fillet is provided between the members along the line of intersection thereof and of such size-as to substantially maintain the section modulus or cross-sectional area of the members constant as viewed in section taken through that portion thereof including said opening; and the provision of a cast metal article including intersecting ribs, webs, bars orother structural elements of substantially equal metal thickness having openings extending through the line of Michigan intersection thereof in a plane perpendicular to the line of intersection, such openings being spaced from one another longitudinally of said line of intersection by a distance approximately equal to the normal 'metal thickness of said members.

The above being among the objects of the present invention thesame consists in certain novel features of construction, combinations of parts and step or steps of operation to be hereinafter described with reference to the accompanying drawing, and then claimed, having the above and other objects in view.

In the accompanying drawing which illustrates suitable embodiments of articles constructed in accordance with the practices of the present invention, and in which like numerals refer to like parts throughout the several different views,

Fig. 1 is a fragmentary partially broken, partially sectioned plan view of a heat treating grid or frame;

Fig. 2 is an enlarged, partially broken, partially sectioned side elevational view of the grid or frame shown in Fig. 1, taken on the line 2-2 of- Fi 1;

Fig. 3 is an enlarged, fragmentary, transverse sectional view taken on the line 3-3 of Fig. 2;

Fig. 4 is an enlarged, fragmentary, partially broken, partially sectioned perspective view taken at the point of junction of two of the webs or bars of the grid or frame shown' in the preceding views to better illustrate the construction of the same;

Fig. 5 is a fragmentary perspective view showing the intersecting area between two webs, bars or the like of a cast article in which the webs or bars have a relatively greater depth than those illustrated in the preceding views;

Fig. 6 is a fragmentary, partially broken, partially sectioned plan view of a modified form of grid structure constructed in accordance with the present invention;

Fig. 7 is an enlarged fragmentary perspective view showing the junction between three of the webs or bars of the construction shown in-Fig. 6; and,

Fig. 8 is a fragmentary perspective view of an elongated bar member formed in accordance with the present invention.

It is well understood in the art that where articles having ribs, braces, bars or other con-v structio'n members which meet or intersect are formed integral from cast metal, a crack is H- able to develop along the line of intersection unless special precautions are taken to avoid it.

A common precaution taken to avoid the occurrence of such cracks is the provision of rounded fillets or radiuses between the members along the line of intersection between them. Precautions are also taken, if at all possible, to make such intersecting ribs, braces, bars or other members of substantially equal thickness, otherwise 'the slower cooling of the thicker sections will promote the occurrence of such cracks. The provision of such fillets or radiuses, even where such members are of substantially equal thickness, introduces a mass of metal at and adjacent the line of intersection-between them which is relatively heavy in comparison with the normal thickness of the members, and this added thickness cools more slowly than the contiguous portions of the memberswith the result that a shrinkage cavity is often and is usually produced within such mass of metal, thus materially weakening the structure.

To avoid the occurrence of such shrinkage cavities which would otherwise be produced by the added mass of material formed by such fillets or radiuses, it has heretofore been the practice to core a hole in the article along and concentric with the line of intersection between the members and'extending between opposite edges of the members, the hole preferably being. of such diameter or other cross-sectional configuration as to maintain a substantially constant wall thickness to all sections of the article taken through the area of intersection between the members thereof.

Where bar-like members intersect in the manner described and form the structuraI elements of a grid or frame. and are provided with such openings extending therethrough in the direction of the line of intersection between the bar-like elements thereof, the grids are not very suitable to carry transverse loading applied in a direction perpendicular to the face of the grid or frame, nor are they very suitable to withstand compression in a direction transverse to such openings. This is particularly true where such grid or frame is subjected in service to relatively high temperatures as, for instance, where it is employed as asupport for articles undergoing a heat treating operation and under which condition the tensile and compressive strength of the materialfrom which the grid or frame is constructed is materially reduced. Regardless of the type of use to which such gn'ds or frames are put, the bending moments in the bar members are liable to distort the ring or tubular intersection which passes through the tension and compression areas of the bar elements. The intersection is also weak under compressive forces acting in the plane of the grid or frame.

It is well known that a ring or tube section interposed in a beam, and carrying a load acrossv it from one side to the other, will tend to flatten or distort. In a grid containing a multiplicity of such intersections, the cumulative efiect of the multiple ring distortions is an appreciable sagging of the grid as a whole, much in excess of the sag which takes place in the grid without ring-like intersections. This sag or deforation is especially noticeable in grids, furnace grates and work supporting trays which operate at elevatedtemperatures. 1

A-method has been discovered in accordance with the present invention for producing intersections without cracks or shrinkage cavities, and such intersections made in accordance with the present invention are not subject to ring pression and shear as a plain rib intersection devoid of cracks or cavities. This result is accomplished by providing such intersections with fillets or radiuses to avoid the occurrence of shrinkage cracks during cooling, and avoids the occurrence of shrinkage cavities by providing openings in the intersecting areas of the bars or ribs, but instead of such openings extending in the direction of the line of intersection of the members as in the prior practice, these openings extend in a direction perpendicular to the direction of the line of intersection. These openings are located intermediate the opposite edges of the members which intersect and are preferably of such dimensions longitudinally of the line of intersection that the thickness of the solid parts of the intersection on opposite sides of such openings and measured in the direction of the line of intersection approximately equals the metal thickness of the members where possible because of the cross-sectional configuration of the members. I'hus, as a matter of illustration, where the bars or ribs are rectangular and are three times as deep as they are thick, a single opening through the intersection midway between the opposite edges of the member may be of a dimension measured along the line of intersection equal to the thickness of the members, and may be located a distance equal to such thickness from the upper and lower edges thereof. This, of course, leaves wall thicknesses extending perpendicularly to the line of intersection of the same thickness as the 'thickness of the intersecting members and eliminates the possibility of occurrence of shrinkage or other cracks or the occurrence of shrinkage cavities. It will, of course, be understood that where the ratio of metal thickness to the depth of the intersecting members is greater than the example given, sufficient numbers of such openings may be provided along the line of intersection between the members to achieve the effect mentioned. The proportions of the cored holes may also be varied.

In order to overcome any weakness along the line of intersection which would otherwise occur by the introduction of the openings therein, the fillets or radiuses provided at the area of intersection between the members, and which in accordance with the present invention take the form of flanges, are preferably of such size as to develop the capacity of the intersecting members in shear, compression and bending to at least ticular grid tray shown is of the reversible type,.

that is either face may be employed as the upper face, although this feature is of no importance as far as the present invention is concerned. Such grid trays are supported by two or more tracks or rails or lines of rollers provided therefor in the annealing furnace, the

particular grid tray shownbeing constructed for use on a pair of suchtrack rails or lines of rollers and for that purpose it is provided with a mediate the channels as the thickness of the ,in accordance with well understood practice.

or web It which extends completely around it,

together with a plurality of longitudinally and a transversely spaced bars or web members I! arranged in spaced relation to each the peripheral bar or web l2 and channel In and extending in parallel relation with respect to the channel ill and the ends of the grid tray respectiveiy. The spacing of the longitudinally extending bars or webs it may be equal to the spacing of the transversely extendingbars or webs M, or the spacing of the former may be difierent from the spacing of the latter, the transversely extending bars or webs being spaced from each other a slightly greater distance than the longitudinally extending bars or webs in the particular embodiment shown. Fillets or radiuses is are provided between all of the members at their points of intersection-with each other as illustrated. Although the cross-sectional con figuration of the bars or other intersecting members may be of any shape and proportions desired, and the depth of one of two intersecting members may be greater than the other in the practice of the present invention, for the purpose of explanation it may be noted that in the particular construction shown the peripheral bar 12 is of the same depth as the bars l4 except across the opposite ends of the grid tray inter- Hi and over the width of which it is cut away to continue the grooves of the channels out through the end of, the grid tray, and except at intervals along the length of its sides where occasional vertical projections 58 are provided for the purpose of retaining loose containers loaded on the tray. The bars l4 and the bar H! are all of substantially the same thickness and the web and flanges of the channels ID are of substantially the same thickness bars I4. This feature is It will be understood that if the grid tray illustrated were provided with the conventional ring type intersections between the members or bars l4, channels I 0, and bar l2, circularly or other sectioned openings would be cored on the line of intersection between these bars or other members. Consequently, if the grid tray were supported through the channel) on a pair of tracks and the weight were applied to the upper surface of the grid tray between the tracks, these openings would tend to be compressed transversely of the grid on the of the same and to be elongated transversely of the grid on the lower surface of the same, the cumulative effect of such compression and elongation of the openings-at the intersection of the various members between the channels l causing a decided sag in the central portion of the grid tray. This efiect is, of course, more pronounced at elevated temperatures when the material from which the grid tray is formed has a tensile and compressive strength is subject to creep or permanent deformation under normal stress and does oifer a serious problem in such grid tray. v

On the other hand, unless the fillets I6 are provided, cracks will develop in the castings and I the lines of intersections between the bar members I4 and the other are, provided and no members and if the fillets openings provided in the other and to horizontal sections taken upper surface casting, in providing sections of equal thickness will be thickened section thus provided, the excess metal at such intersections in cooling will cause cavities to be internally formed therein which cavities materially weaken the strength of the section.

.In accordance with the present invention, in order to eliminate the possible occurrence of cracks at the lines of intersection of the various members, the fillets 16 are provided, and in order to eliminate the occurrence of cavities over the intersecting areas and yet avoid the disadvantages inherent in providing openings extending through the grid trays along the line of intersection of the various members,'openings 20 are provided. The openings 20, instead of extending along the line of intersection of the members'from one face of the grid tray to the other, extend transversely to the line of intersection and are located between the opposite faces of the grid tray. These openings 20 must, of course, be formed in theprocess of casting the grid tray and not machined therein after otherwise the advantages of the same lost.

The employment of the openings 20 provides a construction in which the bars l4 and other members connected to the bars M are continuous and unbroken inhorizontal section taken through certain levels of the area of intersection between them but are interrupted or broken in other at other vertical levels therethrough. The openings 20 are so spaced from the top and bottom surfaces of the grid tray that the thickness of the wall of metal left above and below them is preferably substantially equal to the thicknessof the bars 14, and

where two or more openings are provided over the length of the line of intersection between two such members, the vertical dimensions of the openings are such as to provide an intervening wall section between them of substantially equal thickness to the bar members I I. In the particular embodiment shown, the bar members l4 are of a thickness substantially one-third the depth thereof so that where one opening is provided in each intersection it will be located midway between the top and bottom faces of the grid tray and be of a vertical dimension equal to the thickness of the bars I 4. The depth and the number or openings 20 employed will, of course, vary according to the relative depth of bar members such'as the bar members M with respect to the thickness thereof. For instance, if the depth of bar members M was only two and one-half times the thickness thereof, then the vertical dimension ofthe single opening 20 provided in accordance with the present invention might be one-half of the thickness of the bar members M to achieve the desired result but subject to a minimum desirable core thickness. On the other hand, if the depth of the bar members I4 was three and one-half times the thickness of the bar members, then the vertical dimen- -As best brought out in Fig. 3, in forming the openings 20, which, of course, are formed by the provision of suitable cores in the mold in which the grid tray is cast is readily understood by those skilled in the art, and where the bar members form an X-typeintersection, the ends of each pair of intersecting bar members M are extended inwardly toward the line of intersection between them beyond the outer margins of the corresponding opening 2! where it extends outwardly into e associated. fillets I8. Such inwardly proiecting ends are preferably rounded off to semi-cylindrical shape as indicated about an axis parallel to the axis. of the intersection of the bar members I.

The preferable proportions of the parts at the various intersections between the bar members in the particular tray shown by way of illustration are indicated in Fig. 3, in which the thickness of the bar members is indicated at t". The fillet I6 preferably has a radius equal to 2t" and the distance between the axes of adjacent semi-cylindrical ends of the ,bars ll is preferably equal to 2t. Where such proportions are maintained it will be found that the bending strengthof the sections taken along either of the bar members 14- and in the plane of the depth thereof is substantially equal to that of solid bars intersecting each other without the employment of fillets and with an intersection devoid of cracks or cavities. Because of the use of the fillets I6, the strength of the bars to compression along their length and to shear is not diminished as compared to the strength of bars such as ll which intersect solidly with one another without the use of fillets and with an intersection devoid of cracks or cavities. Because of the fact that the openings 20 do not extend throughout the depth of the grid tray, solid, horizontally directed sections are provided at the upper and lower faces of the grid tray, and in planes intermediate thereof where more than one opening is provided in each intersection, which thus eliminates horizontally distortable sections as occurs in ring type intersections and thus eliminates the sagging tendencies inherently found in such ring type intersections. Nevertheless, all of the wall sections provided in the intersecting area of the bar members in accordance with the present invention are of equal thickness, thus insuring uniform cooling and absence of cracks or cavities in the area. The advantages of the present invention will, therefore, be apparent.

Where bar members meet to form a T, as for instance where the transverse bar members l4 meet the flanges of the channel ll, the advantages of the present invention are obtained by providing openings such as 22 at the intersecting area between them. The openings 22, as best illustrated in Fig. l, are in such case provided in the bar member H and fillets l6 only, this being for the purpose of preserving the desired wall thickness in the member forming the head of the T. The openings 22 are, of course, positioned longitudinally of the line of intersection between the members in the same manner as the openings 20 above described. The results obtained are, of course, the same as the results obtained as above described in connection with the openings 20.

In Fig. 5, a construction is shown which may be assumed to be, for instance, a part of the grid structure of the same general type as illustrated in the preceding views and, accordingly,

the bar members corresponding to the bafmembers M are illustrated at Ila and as having fillets "a corresponding to the fillets I! between them. In this case, the depth of the bar members a is assumed to be about five times the thickness of the bar members and, accordinz y.

in order not to unduly weaken the intersection between the barmembers by the employment of an unusually deep opening therethrough. two openings 20a, each corresponding to the openings 20, previously described, are employed, each opening 20a being of a vertical dimension approximately equal to the thickness of the bar members a and being spaced from one another and from the corresponding top and bottom surfaces of the grid tray by a distance equal to the thickness of the bar members Ma. It will be appreciated that this construction provides walls of sensibly equal thickness throughout the intersection and incorporates, all of the advantages provided by the previously described construction.

In Figs. 6 and I, a grid of different configuration is illustrated to indicate that the application of the present invention is not limited to grid structures in which the various elements 'or bar members thereof intersect in perpendicular relationship to each other. In this particular case, the grid structure is integral as in the first described construction and includes a plurality of relatively short bar members 30 arranged to form openings of hexagonal nature between them. Thus, three bar members 30 intersect along a common line, and an opening 32 extending transversely to the line of intersection between the members 30 is provided in the area of intersection of such members as best shown in Fig. 7. It will be understood that the opening 30 is positioned in the same relationship with respect to the top and bottom faces of the grids in Figs. '7 and 8, as in the first described construction, and that equivalent results are, therefore, obtained by the use of the same.

It is not to be understood that the present invention is limited. entirely in this application to so-called grid structures, as obviously some if not all its advantageswill be realized in any device of integral cast construction where ribs; webs, bars, or other structural elements intersect one another. For instance, a construction is illustrated in Fig. 8 which may, for instance.

be a supporting member, a grate bar in a furnace, or other suitable element. The device illustrated in Fig. 8 may be considered as being made up of two webs or bars 40 intersecting each other along their central axis and arranged to form a member of X cross-section. In such case, fillets 42, corresponding to the fillets l6 previously described, ar preferably provided at the junction of the webs or bars. Openings ll, corresponding to the openings 20, 20a, and 32 previously described, are provided in the member and extend therethrough transversely of the direction of the line of intersection of the bars or webs thereof, the openings 44 preferably being spaced from one another by a distance such as to leave a transverse web of a thickness equal to the thickness of the webs or bars 40 extending transversely between them. I

It will, of course, be understood by those skilled in the art that there may be occasions when an axial opening through the line of intersection of members as contemplated herein will be desirable or necessary in addition to the transverse opening tures or the like are to be supported on a tray of the type described, this offering no problem if the fillets or radii are increased in size to compensate for the metal removed by the axial openings.

With the'teachlngs herein given, those skilled in the art will appreciate the application of the present invention to various types and arrangements of intersecting members in cast constructions and, accordingly, it will be understood that formal changes may be made in the specific embodiment of the invention described without departing from the spirit or substance of the broad of intersection.

invention, the scope of which is commensurate with the appended claims.

What I claim is:

1. In combination, a pair of cast metal bar members each having a dimension measured transversely thereof greater in one direction than in a direction transversely thereof and perpendicular to the first mentioned direction, said members being integral and intersecting one another, at least one of said members having an opening cast therein extending therethrough transversely to the line of intersection between said members and located intermediate the edges of said members at opposite ends of said line of intersection, said opening being of an extent longitudinally of the member through which it extends approximately no greater than the area of intersection of said members and being spaced from at least one of said edges by a distance substantially equal to the metal thickness of said members.

2. In combination, a plurality of integrally cast metallic bar-like members intersecting one another in X-shape formation, fillets integral with said members at the area of Junction thereof, said members being of a greater dimension measured in one direction transverse to the length thereof than the transverse dimension thereof in a direction perpendicular thereto, and said members having at least one opening cast therein intermediate the length of the line of intersection between them and extending therethrough and through said fillets in a direction perpendicular to said line of intersection, said openings being of approximately no greater dimension in the direction of length of said members than the area of intersection of said members,

3. In combination, a plurality of integrally cast metallic bar-like members intersecting one another in X-shape formation, fillets integral with said members at the area of junction thereof. said members being of a greater dimension measured in one direction transverse to the length thereof than the transverse dimension thereof in 5. An integral cast metal grid structure or the like comprising a plurality of bar-like members of greater depth than thickness arranged in intersecting X-shaped relationship, at least two of said intersecting members having an opening therein confined approximately to the area of intersection between them and located intermediate the length of the line of intersection between them and extending therethrough in a direction perpendicular to said line of intersection, said opening being spaced from by a distance substantially equal to the metal thickness of said members.

6. An integral cast metal grid structure or the like comprising. a plurality of bar-like members of greater depth than thickness arranged in intersecting X-shaped relationship, fillets formed between adjacent faces of said intersecting members, at least two of said intersecting members having an opening therein intermediate the length of the line of intersection between them and extending therethrough and through said fillets in a direction perpendicular to said line of intersection.

7. In the formation of an integral cast metal structure including a pairv of intersecting bar members arranged in Xsshaped relationship and of greater transverse dimension in one direction than in a direction perpendicular thereto, the method oi eliminating cracks and cavities in said members along the line of intersection between them comprising the step of forming, during the a direction perpendicular thereto, and said memlbers having at least one opening cast therein intermediate the length of the line of intersection between them and extending therethrough and through said fillets in a direction perpendicular to said line of intersection and of a size transversely of said line of intersection approximately within the filleted area of said intersection, said opening being so positioned along said line of intersection as to leave a transverse web between it and an edge ofsaid member substantially equal in thickness to the metal thickness of said member.

4. An integral cast metal grid structure or the like comprising a plurality of similarly dimencasting operation, an opening therethrough intermediate the length of line of intersection betweeen them and extending in a plane perpendicular to said line of intersection, the extent of said opening-.iongitudinally of said members being confined to approximately the area of intersection between said members.

8. The method of eliminating cracks and cavities in the area of intersection between a pair of intersecting bar members of cast integral construction arranged in X-shaped relationship comprising thestep of forming, during the casting operation, an opening through said members extending approximately only over the areaof intersection thereof intermediate the opposite edge faces of said members and extending in a direction perpendicular to said line of intersection.

9. In combination, a pair of integral cast metal bar-like members each of greater depth than width arranged in iniersectingrelationship and with the direction of their depth perpendicular to a plane parallel to the longitudinal center lines of both. said members having an opening extending transversely therethrough at the line of intersection thereof and intermediate the opposite ends of said line of intersection, said opening being limited in extent longitudinally of said members to approximately the areas of intersection thereof.

ARTHUR, 1*. .IB. THOMPSON.

a face of said grid 

